Michigan’s Jim Harbaugh has a habit of staying at each of his coaching stops only four years at a time. University of San Diego, four years. Stanford, four years. 49ers, four years.

But none of those tenures ended because Harbaugh was struggling. To the contrary, he has consistently performed well. The bar, however, rests much higher at Michigan, where many believed that Harbaugh would become Schembechler 2.0 for the Wolverines.

The honeymoon ended a while ago, and the criticism is becoming more pointed in the wake of Saturday’s loss at Wisconsin.

“This is Michigan football right now,” writes Nick Baumgardner of the Detroit Free Press. “A team that’s not ready to sit at the big table. A coaching staff that has a lot of questions to answer. A program that’s got a long way to go.”

The overriding question is how much longer will Harbaugh be the person guiding the program? He continues to be linked via rumors, speculation, and open longing to the Bears. The Colts get mentioned from time to time as well, a move that would reunite him with Andrew Luck — but that also would require Harbaugh to tolerate Jim Irsay.

It’s premature to consider the possibility of Michigan firing Harbaugh. However, he may be starting to consider whether he should walk well before the point where they make him run.